1. Field of the Invention
The present invention relates to a probe apparatus for measuring electrical characteristics of an object such as a semiconductor wafer on which a plurality of semiconductor devices are formed or a glass substrate on which pixel drive circuits constituting a liquid crystal device are formed, and more particularly to a probe apparatus characterized by a probe card holder for holding a probe card.
2. Description of the Related Art
As is well known, a great number of semiconductor devices are formed on a semiconductor wafer by employing precise photographic transfer techniques, and the wafer is cut to separate individual semiconductor devices. In a conventional process of manufacturing such semiconductor devices, a probe apparatus is used to test and evaluate electrical characteristics of semi-finished semiconductor devices as formed on the semiconductor wafer. Only a semiconductor wafer, the condition of which has been judged to be good, is subjected to a subsequent step such as packaging, thereby enhancing productivity.
The probe apparatus includes a wafer table which is movable in X-, Y-, Z- and .theta.-directions. A probe card having many probes corresponding to electrode pads of semiconductor devices is fixed above the wafer table by means of a suitable probe holder. When measurement is performed, an object such as a semiconductor wafer is placed and fixed on the wafer table, and the wafer table is moved such that the probe needles are put in contact with the electrodes of the semiconductor devices. The semiconductor devices are tested via the probes.
In a probe test, it is desirable that data items peculiar to probe cards, such as type numbers, the number of times of use, etc., be managed on a card-by-card basis. Thus, it has been proposed to provide a memory device for memorizing such data above the probe card (Published Unexamined Japanese Utility Model Application (PUJUMA No. 59-3537).
However, since the integration density on the semiconductor wafer has been increased, as mentioned above, it is necessary to arrange 1000 to 3000 probes on a probe card constituted by a printed circuit board and to provide wiring areas associated with the probes and land areas for contact with a tester. It is difficult to find a room for providing the above-mentioned memory device on each probe card having 1000 to 3000 probes and electrodes for providing electric lead wires of these probes. Even if it is possible to provide the memory device on the probe card, the memory device may be affected by noise or crosstalk from the probe card, and the exact operation of the memory device cannot be ensured. Furthermore, measurement signals which are processed at high speed via the probes may be adversely affected. Thus, it is desired to provide the memory device in such a position as to be movable with the probe card, without such adverse affection.
On the other hand, according to modern art relating to the probe apparatus of the above type, the contact between each probe on the probe card and the tester is effected by a pogo contact technique wherein spring-urged contact pins (pogo pins) are put in pressure contact with electrode land areas connected by electric lead wires. As regards this technique, for example, in the case where 100 probe needles are put in contact with the tester during tests, if a force of about 10 g is exerted on each probe, a force of about 1 kg is exerted on the entire probe card.
In particular, with higher integration of semiconductor devices in, e.g. a CPU of a supercomputer, the number of probes necessary for testing one chip increases more and more. Recently, in the field of semiconductor manufacture, there is a demand for the above-mentioned probe card having 1000 to 3000 probes, and in some cases such many probe needles are provided in a very small region of, e.g. 2 cm.times.2 cm. In such a case, a force of 10 kg to 30 kg is applied to the entire probe card. When a force of a predetermined value or more is exerted on a probe card, the probe card is deformed in a Z-direction in accordance with the exerted force. If such a great force is exerted, the degree of deformation or strain is very high and the probes cannot be put in contact with the object with uniform pressure and uniform parallelism. Consequently, exact tests are not performed. To solve this problem, some techniques have been proposed to increase the strain-resistant properties of the probe card itself, but there is a limit to such techniques and there is a demand for advent of novel techniques.
In addition, there has recently been put into practice a method of measuring electrical characteristics of a semiconductor wafer at high temperatures by heating the wafer from room temperature up to about 150.degree. C. by means of a table on which the wafer is placed. In the case of such high-temperature measurement, a probe card holder formed of a metallic member such as stainless steel or aluminum, which tends to be more thermally deformable than the probe card, is considerably deformed, and the probes are not put in contact with the object with uniform pressure and uniform parallelism. Consequently, exact tests cannot be performed. Therefore, it is desired to enhance the strain-resistant characteristics of the probe card holder for the purpose of high-temperature measurement.